Healthy myocardium responds to pathologic stress with alteration of cardiac structure and hemodynamic performance associated with increases in proteins primarily associated with embryonic and fetal development. While such chronic changes may be considered compensatory, they are not directed at repairing underlying acute damage or targeting cellular wound healing upon focal sites of trauma. Induction and/or potentiation of myocardial healing represent novel approaches to treatment of pathological insults. In turn, enhancement of reparative and/or regenerative mechanisms depends upon delineation of processes that regulate cellular and molecular responses. The long term goal of this study is to understand molecular mechanism(s) responsible for reparative and regenerative signaling in the myocardium. The goal of this proposal is to demonstrate that myocardial regeneration and repair depends upon two stem cell-associated signaling pathways expressed in injured myocardium that are critical regulators of cellular proliferation and survival: Notch and nucleostemin. Specifically, experiments are designed to optimize myocardial repair and regeneration. The hypothesis is that activation of regenerative signals promotes a combination of enhanced survival and/or proliferation as well as enabling communication between cardiac stem cells and the myocardium. Specific aims will demonstrate that: 1) injury or stress stimuli in the heart promote increased expression and activation of regenerative signaling, 2) survival and proliferation of myocardial lineage cells in the damaged myocardium are enhanced by regenerative signaling activity, 3) survival and proliferative signaling effectors in myocardial lineage cells are regulated by regenerative signaling cascades, and 4) cellular commitment and myocardial repair are facilitated by regenerative signaling cascades. The innovative approach employed will involve molecular, biochemical, and microscopic analyses of cultured cardiomyocytes and mouse models manipulated to optimize Notch and nucleostemin activity via cardioprotective stimuli, recombinant adenoviruses, and genetically engineered transgenic mouse lines. The significance of these studies is to establish mechanism(s) of regenerative signaling that occur in pathologically challenged cardiomyocytes, to understand the role of these canonical regenerative signaling pathways in the context of the myocardium, to establish relevance of these regenerative cascades for potentiation of cardiomyocyte proliferation and survival, and to delineate the basis for how cardiomyocyte-autonomous stem cell signaling facilitates communication with local stem cell populations.